1. Field of Invention
The invention relates to a flow-guiding device and a fan assembly. In particular, the invention relates to a flow-guiding device and a fan assembly with better efficiency.
2. Related Art
As electronic devices have better performance, operate at higher frequencies and speeds, and become more compact, they generally generate more heat. They are therefore likely to be unstable, lowering the reliability thereof. Therefore, heat dissipation is an important issue of the field. Using the fan as a heat dissipating device is a common solution. To enhance heat dissipation, several fans are often connected in series.
As shown in FIG. 1, a conventional fan assembly 1 consists of an above fan 11 and a below fan 12 connected in series. The above fan 11 has a fan frame 111 and an impeller 112 disposed inside the fan frame 111. It also has several blades 1121 and a hub 1122 connected with each other. The above fan 11 further has several static blades 113 connected with the fan frame 111. The below fan 12 also has a fan frame 121, an impeller 122, and several static blades 123. The impeller 122 also has several blades 1221 and a hub 1222. The structure of the below fan 12 is the same as the above fan 11. They rotate in the same direction (as indicated by the arrow in FIG. 1). The fan assembly 1 is shown in FIG. 2.
The airflow in the fan assembly 1 is illustrated in FIG. 3, where the rotation direction R of the blades is also indicated. When the above fan 11 rotates, airflow goes from the blades 1121 to the static blades 113. Once the airflow is guided by the static blades 113 to the below fan 12, it goes to the low pressure area L of the blades 1221. This reduces the pressure difference between the high pressure area H and the low pressure area L of the blades 1221. Moreover, the airflow guided by the static blades is almost perpendicular to the blades 1221. These factors greatly reduce the efficiency of the below fan 12. Therefore, the air pressure and quantity output by the fan assembly are reduced.